My bad, I failed to mention it since I didsn't realise it was relevant.
I've run the suggested commands, didn't help.
I don't have access to the install disk atm (in school) but will try in a few weeks when I go back home. My comp isn't critical as I have a laptop backup, and can use cmd to get files from comp onto a USB.
Cheap PSU was my Dad's idea - apparently there's no point getting a good one. I didn't and still don't agree, but I couldn't persuade him. I did speak to him, he suggested that my SSD was corrupted. Fresh install may be my only option.